Add.
Solution: There are many ways to solve this problem. Let's see two ways we can solve it. Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths $8$ ${0}$ $.$ ${0}$ $7$ $.$ ${1}$ Because ${80}$ is a whole number, we can add a decimal point and a $0$ behind to make the columns align. Now, let's add each place value column. Tens Ones $.$ Tenths $8$ ${0}$ $.$ ${0}$ $+$ ${7}$ $.$ ${1}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $8$ $7$ $.$ $1$ Decomposing the numbers We can group the whole numbers together and the decimals together. $\begin{aligned} &({80} + {7}) + {0.1}\\\\ &=87 + {0.1}\\\\ &=87.1 \end{aligned}$ $87.1 = 80 + 7.1$